פירוש על עבודה זרה 31:16

The Talmud raises a difficulty on anyone who says it is prohibited to sell them large wild beasts. Large wild beasts may not be sold only if they present a danger to the public. But if they are not dangerous, then they may be sold to them.

Rabbah b. Ulla explains that the Mishnah prohibits selling a mutilated lion which is not fit for work, and it follows the opinion of R. Judah from the previous mishnah who forbade selling maimed animals. But an unmaimed large wild animal would be prohibited, even according to the other rabbis, even if it does not present a danger to the public.
Ashi says that all lions are considered “maimed” when it comes to work. After all, a lion cannot be put to work. Thus a lion that does not present a danger could be sold. But a different wild animal that can do work cannot be sold under any circumstance.